Car lighting system



"NOV. 6, 1934. W N

' CAR LIGHTING SYSTEM Filed Sept. 12. 1931 WI TNESSES Patented Nov. 6,1934

CAR LIGHTING SYSTEM Thomas S. Watson, Milwaukee, Wis., assignor to Car Lighting Improvement Company, Milwaukee, Wis., a corporation of Wisconsin Application September 12, 1931, Serial No. 562,523

' j 1 Claim., (01. 171-313) The invention relates to -car. lighting systems.

' "It has heretofore been proposed to provide a car lighting system including a plurality of seriesconnected lowvoltage incandescent lamps each 5 of which upon'iailure is automatically short-cirjcuited or by-passed in order to maintain the circuit closedthrough the remaining lamps, shortcircuiting lamp sockets being also provided to permit replacement of lamps'without opening the lamp circuit. With this arrangement, the failure of a lamp will reduce theresistance of the lamp circuit and correspondinglydncrease "the lamp current, which is" undesirable although not serious to the life of the remaining lamps if the damaged lampis promptly replaced. Experience has shown, however, that car crews do not make replacements promptly, thus favoring the "premature destruction of the remaining lamps .by excessive current. If'two or more lamps are permitted to remain in short-circuited or by-passed condition, the life .of the remaining lamps may become quite limited;

It is an object of the present invention t0.pro vide a carlighting system includingfseries-com' 'nectec1 incandescent lamps of the automatic cut-' out type and including means for maintaining the lamp current substantially constant notwithstanding the failure and short-circuiting of one or more lamps or fluctuation of the supply voltage.

The invention further consists in the several features hereinafter set forth and more particularly defined by the annexed claim.

In the accompanying drawing, Fig. 1 is a schematic diagram of a car lighting system embodying the invention; v

Fig. 2 is another schematic diagram showing the relay connections, and

Fig. 3 is a detail view of one of the relays, parts being broken away and parts being shown in section.

In the drawing, the numeral 10 designates of each relay are connected in series, in such a way as to give a cumulative magnetic effect. The winding 19 is also connected so as to be cumulative with 16 and 17 when it is in circuit. The

56 relative magnetic pull of the windings and the 21, 22, 23, 24, and 25. The windings 16 and'l'l tension on the spring of the relay armature are such that the armature will not lift with less than an excessive current in the winding 17 only, but will lift when the current is about 4% above normal in the combined windings 16 and 17, and, having lifted, will drop when the current is about 4% below normal in the windings 16 and 17. In other words, the relay is sensitive to open or close the switch 20, with windings l6 and 17 in circuit. When winding 19 is in circuit with its cumulative action, the armature will not drop until the current has fallen to the order of of normal, that is, the switch 20 will be locked open, and the relay is not sensitive with winding 19 in'circuit. 70

.Thevload circuit is supplied with current from supply mains, here indicated to be trolley wire 26 and a ground return 27. A current collector 28 engages the trolley wire and is connected by a conductor 29 to the winding 16 of the relay 11. The conductor 28 may include a circuit-breaker 30 and a switch 31. The winding 16 of the relay 11 remains in circuit at all times. The winding 17 is connected by a conductor 32 to one terminal of the switch 20, the other terminal of which is connected by a conductor 33 to the junction of the windings l6 and 17 of the relay 12. The conductor 32 joins a conductor 34 leading to one terminal of the resistor 21, the other terminal of which is connected by a conductor 35 to the winding 16 of the relay 12. The resistor 21 and the winding 16 of the relay 12 are thus connected in series and are normally short-circuited by the switch 20. The conductor 32 of the relay 12 is connected by a conductor 36 with one end of the winding 19 of the relay 11, and the other end of this winding is connected by a conductor 37 with one terminal of the resistor 22. The winding 19 of relay 11, the resistor 22, and the winding 16 of the relay 13 are thus connected in series and are normally short-circuited by the switch 20 of the relay 12. The remaining relays are similarly connected except that the Winding 19 of the last relay (relay 15) is inactive or may be omitted. The switch 20 of the relay 15 is connected by a conductor 38 to one terminal of the resistor 25 and their junction is connected by a conductor 39 of a lamp circuit consisting of a single series of automatic cut-out incandescent lamps 40 which become automatically short-circuited or bypassed when they burn out, thereby avoiding interruption of the lamp circuit. The last lamp 40 is connected to the ground return 27 and is one of two lamps for the headlights which are alternatively placed in the series by a switch 41. The

lamps 40 and 40 are of a low voltage type having the same current rating, although they may have different voltage ratings to obtain the desired candlepower. The lamps for general illumination within the car are preferably of higher voltage rating to permit comfortable reading, while other lamps for signs, route markers, signals, etc.,'

are preferably of lower voltage rating and therefore of lower candlepower. The use of a single series lamp circuit materially simplifies the car wiring.

When a lamp burns out and is automatically short-circuited or by-passed, the resistance of the lamp circuit decreases, which tends to increase the current through the lamps; However, the operation of the regulator is such as to maintain the lamp current substantially constant under both a variable lamp circuit resistance or a variable voltageon the supply mains. When the line voltage is low, all the switches of the several relays are closed and current flows from the trolley wire through the current collector 28, conductor 29, the series-connected windings 16 and 17 of the relay 11, through the closed switch 20, the winding 17 of the relay 12, the closed switch 20 of the relay 12, through the series-connected windings 17 and switches 20 of the remaining relays in the same manner, conductors 38 and 39, series-connected lamps 40, switch 41, one of the headlight lamps crease of current by including its winding 16 in circuit with its winding 1'7, as previously explained. The switch 20 of the relay 11 does not close when the current drops to normal value. A further slight increase of current will open the switch 20 of the relay 12, thus diverting the lamp current through the conductor 36, the winding 19 of the relay 11, conductor 37, resistor 22, and the winding 16 of the relay 13 to restore the current to its normal value, the remaining path of the current being unchanged. The lamp current. flowing through the winding 19 locks therelay 11 and makes it insensitive to current changes. Further slight increases in current incident to reduction in lamp circuit resistance or increase in line voltage will progressively omrate the remaining relays in the same manner to again restore the lamp current to normal value. Upon a reduction in line voltage or an increase in lamp circuit resistance incident to the replacement of a burnt-out lamp, the lamp current will decrease slightly from normal and the relayswill operate progressively in a reverse direction to close the resistor short-circuiting switches and restore the lamp current to its normal value. As each relay switch closes, the winding 19 of the preceding relay is deenergized and this relay is thereby rendered sensitive to a decrease in current. The relays are uniformly adjusted.

' The lamp circuit is designed so that the lamps will light to normal brilliancy on the lowest voltage met on the line, any excess of voltage being absorbed in the regulator resistors when the line voltage increases. This permits good lighting and comfortable reading on all parts of the line, even though the line voltage is reduced during rush periods and in congested districts to obtain power economy. The lamps are preferably of a high efficiency gas-filled type, which necessarily operate at a high filament temperature. This condition inherently lowers the margin of over-voltage at which the lamps may operate with a reasonable length of life, but since the regulator maintains the lamp current substantially constant the lamps will have their normal service life.

Because a considerable number of the seriesconnected relay windings remain continuously in circuit, they provide a choke coil action which reduces the efiect on the lamps of voltage surges on the line, such as lightning surges, thereby protecting the lamps against burn-out. Since the failure and short-circuiting of a lamp, after it has burned its normal life, does not result in an increase of current through the remaining lamps, it is not necessary for the lamp to be replaced while the car is on a run, and the daily inspection in the barns is all that is required. The loss of lamps from theft is greatly reduced, as the low voltage lamps are useless on other circuits.

What I claim as new and desire to secure by Letters Patent is:

In a car lighting system, in combination, a supply circuit, a work circuit having series-connected automatic cut-out incandescent lamps and therefore of variable resistance, a plurality of resistors in series with the work circuit, a regulator sensitive to changes in current flow through the work circuit, and means controlled by said regulator for including in circuit one or more of said resistors to' compensate for a reduction of resistancein said work circuit and to thereby maintain the current in said work circuit approximately constant, said regulator comprising a plurality of resistor-controlling relays operable progressively, each relay having an energizing series winding, at least some of said relays each having a sensitizing series winding rendered effective by THOMAS s. WATSON. 

